Week 1: Respiratory Microanatomy Flashcards
Basic components of conducting division of respiratory track
- nasal passages, pharynx, larynx, trachea, bronchi, bronchioles
- function: filtering, moistening, and warming the air
Basic components of respiratory division of respiratory track
- respiratory bronchioles, alveolar ducts, and alveoli
- where gas exchange occurs
Components of respiratory epithelium
Lines most of the surface of conducting portion of respiratory system. It is a pseudo stratified columnar ciliated epithelium
- ciliated columnar cells: predominant cell type
- goblet cells: secret mucus
- basal stem cells
- enteroendocrine cells: local neuroendochrine function
- brush cells: apical microvilli
Three regions of the nasal cavity
- Nasal vestibule: keratinized stratified squamous epithelium
- Respiratory region: respiratory epithelium.
- lamina propria w/ seromucous glands and vascular supply. Igs, lyzozymes, antibacterial enzymes
- vascular plexi: heat exchanges to warm and humidify air, engorge w/ blood on alternate sides of nose to reduce airflow on one side transiently. prevents drying out, seepage of plasma and seromucous secretions rehydrate - Olfactory region
- olfactory epithelium, lacks mucous glands, bundles of unmyelinated nerves
- bowman’s glands: dissolves odorants to facilitate odor detection
- olfactory neurons
- Sustentacular (supporting) cells: columnar cells with apical microvilli
- basal cells: can become olfactory or sustentacular cells
paranasal sinuses
- maxilla
- frontal
- sphenoid
- ethmoid
structure of salivary glands
-numerous lobules containing acini
-two types of acini: serous (watery, protein) and mucous (viscous, glycoproteins)
-Myoepithelial cells: surround acini and aid in secretion
-IDing gland: parotid (serous), submandibular (mostly serous, some mucous), sublingual (mostly mucous, some serous)
DUCTS
-intercalated ducts: simple cuboidal epithelium. Releases bicarb, absorbs chloride. Drain into striated ducts
-striated ducts: simple columnar epithelium with various infoldings and mitochondria
-excretory ducts: largest and final segment. Transport saliva to oral cavity
Microanatomy of The pharynx: divisions
-nasopharynx: respiratory epithelium
-oropharynx and laryngopharynx: non-keratinized, stratified squamous epithelium
contains seromucous glands and lymphoid tissue
Microanatomy of the larynx
functions: phonation and preventing entry of food or water to lower respiratory passages
- cough reflex
- hyaline cartilage reinforces the wall
- vestibular (false folds): lamina propria contains seromucous glands, adipose cells and lymphoid tissue
- true vocal folds: skeletal muscle and dCT
- mostly respiratory epithelium, but has abrupt transition to stratified squamous epithelium over vocal folds. increased propensity for cancer to develop in regions of abrupt epithelial change
Microanatomy of the Trachea
- rings of c shaped hyaline cartilage with opened ends posteriorly
- lined with respiratory epithelium
- thick basement membrane
- lamina propria: loose CT with many lymphoid elements
- seromucous glands
- hylaine cartilage deep to mucosa
microananatomy of the bronchi
- extrapulmonary bronchi similar to trachea
- intrapulmonary bronchi have irregular plates of hyaline cartilage: Only airway with hyaline
- bronchi lined by respiratory epithelium. Elastic fibers in lamina propria and seromucosa. Lymphoid in both as well. Smooth muscle between lamina propria and respiratory epithelium
Describe micro anatomy changes from bronchus to alveolus as airways decrease in size
- bronchus: hyaline, glands
- bronchiolus: moves to simple cuboidal epithelium, lose goblet cells and glands
-Clara cells - alveolus: simple squamous epithelium
Generally: reduction in height of epithelium, decrease in glands and goblet cells, increase in smooth muscle and elastic fibers as we go from large to small airways
Clara cells
- unique to bronchioles
- domed shaped apical surface with short blunt microvilli
- produce surfactant like solution that reduces the surface tension of the bronchioles and maintains their latency
- secretory proteins: protect epithelium and detoxifies harmful substances
- can multiply and differentiate into ciliated and non ciliated epithelial cells
Microanatomy of alveoli: cell types
-arranged in ducts (linear) and sacs (clusters)
TYPE I ALVEOLAR CELLS
-made up 45% of cells but lines 90% of alveolar surface
-attenuated cytoplasm
-adjacent cells form occluding junctions, preventing seepage of extracellular fluid into alveolar lumen
TYPE II ALVEOLAR CELLS
-more numerous, lines only 10% of alveolar surface
-function: secrete surfactant that forms monolayer on surface that reduces surface tension
-multilammellar bodies in cytoplasm: contains pulmonary surfactant
-stem cells: can replace type I cells after injury (respiratory distress syndrome: when alveoli have insufficient surfactant, too few type II cells)
ALVEOLAR MACROPHAGES
-derived from blood monocytes
-phagocytose particular matter and microorganisms
Blood-air barrier
- capillary endothelium, attenuated cytoplasm of Type I cells, fused basal laminas produced by each cell
- water can’t diffuse across barrier
- alcohol and some organic compounds can
